1. Field of the Invention
The present invention relates to a storage system and a method of controlling a storage system, and particularly relates to low power consumption control technology for a plurality of disk drives of a storage system.
2. Description of Related Art
The increase in scale of data centers presents problems with regards to increases in power consumed by systems and heat emitted by systems. As a result, a storage system is demanded that is capable of consuming little power, and is capable of storing large volumes of data in an effective manner.
Technology for suppressing power consumption of a storage apparatus is disclosed in patent document 1 listed below. The storage apparatus in patent document 1 suppresses power consumption by stopping the supply of power to some hard disk drives (HDD) when load information based on access requests from a host computer falls below a threshold value.
Further, technology for compressing and storing data in a storage apparatus is disclosed in patent document 2 listed below.
However, with data compression technology, it is difficult predict the size of data that is compressed up to the actual execution of compression processing on the data. In addition, there is also the possibility, depending on the data, of the size of the data being larger than that for before the application of compression processing.
[Patent Document 1]
    Japanese Patent Laid-open Publication No. 2002-297320.[Patent Document 2]    Japanese Patent Laid-open Publication No. H05-73213.
With technology such as disclosed in patent document 1 where consumption of power is suppressed by stopping supply of electricity to hard disk drives, in the case of accessing a hard disk that has spun down as a result of a controller stopping the supply of power, it is necessary to wait until the hard disk has been spun up again. Typically, a few seconds to a few tens of seconds are required to spin up a hard disk. As a result, in the event of accessing a spun down hard disk drive, access latency increases dramatically, and there is the fear that this may cause the system to go down.
Further, the storage apparatus disclosed in patent document 2 discloses technology for compressing and storing data but does not refer to the point of suppressing power consumed.
On the other hand, even in the case of using storage apparatus of the same power consumption performance, if a larger volume of data is stored per one storage apparatus, the desired data capacity can be stored using a smaller number of apparatus, which as a result contributes to low power consumption.